Recent advances in consumer appliances have provided additional features to refrigerators which enhance efficiency, ease of use, practicality, or other factors that increase user satisfaction.
As an example, certain refrigerators have recently been designed to provide the option of hot water from a water dispensing system. For example, a refrigerator water dispensing system can include a tank for holding a volume of water and a heating element can be operated to heat the volume of water prior to dispensing the water to the user. More complex implementations, such as instant water heating or on-demand water heating, are available as well.
Most refrigerators also include an evaporator that normally operates at sub-freezing temperatures in a compartment positioned behind the freezer compartment. A layer of frost typically builds up on the surface or coils of the evaporator. Defrost cycles are needed in order to melt any frost or ice that forms or builds upon on the refrigeration coils of the evaporator in a refrigeration system. Typical defrost systems utilize defrost heaters or defrosting elements to melt the ice buildup.
The defrost heater may be similar to the heating elements on an electric stove and can be generally located near or beneath the cooling coils, which are concealed behind a panel in the refrigeration or freezer compartment. During the defrost cycle, the defrost heater gets hot. As a result of its proximity to the cooling coils, any ice or frost build-up on the coils melts. A radiant heater is often positioned inside a housing and below the evaporator to warm the evaporator by both convection and radiant heating in order to quickly defrost the evaporator.
Once a defrost cycle is initiated, it is important to not interrupt the defrost cycle or otherwise cause the defrosting element to lose sufficient power until all of the frost or ice buildup has melted. If the defrost cycle is interrupted while there is still a mixture of frost and water on the evaporator, this mixture will have a tendency to refreeze into solid ice. It is much more difficult to remove solid ice from an evaporator than frost.
Frost tends to be more evenly distributed than solid ice and is less likely to eventually completely insulate the evaporator and reduce or block airflow. Blocked airflow will result in a service call due to lack of cooling. Therefore, an incomplete or interrupted defrost cycle can result in an ice-clogged evaporator.
Thus, a challenge presented by the increasing inclusion of additional features in a refrigerator, such as a water dispensing system that offers heated water, is balancing energy demands from each of such features. In particular, once a defrost cycle has begun, it is important to provide sufficient energy to the defrosting element so that defrosting is properly performed and solid ice is not permitted to form on the evaporator.
Therefore, a refrigerator hot water heater having two energy level settings is desirable.